JEC COMPOSITES MAGAZINE - Issue #73 - June 2012 - 71

micro-pultrusion

Micro-pullwinding and micro-pultrusion – technology and applications
Miniaturized manufacturing techniques for fibrereinforced plastics are still a rather small niche in the composite market. However, the latest developments in micro-pultrusion and micro-pullwinding technologies by the Fraunhofer Institute for Production Technology IPT in Aachen (Germany) offer many new possibilities for the use of fibre-reinforced plastics in diverse applications.

By
prof. Dr.-ing. chriStiAn Brecher, Dr.-ing. michAel emontS, Dipl.-ing. AlexAnDer BrAck, Dipl.-ing. ADriAn Schütte, frAunhofer inStitute for proDuction technology ipt

ultrusion (pulled extrusion) is a well-known process for the continuous production of fibrereinforced plastic (FRP) profiles. It allows the production of profiles with very high and reproducible mechanical properties in a continuous and automated process. Starting with developments for medical applications, the Fraunhofer IPT has miniaturized pultrusion, filament winding and pullwinding processes for fibre-reinforced plastics and automated these technologies. This article shows the technological challenges and the variety of applications involved.

Micro-pultrusion technology
In the pultrusion process, rovings or fabrics are pulled through a resin bath to impregnate them with matrix material. Afterwards, they are pulled through a die to consolidate the fibre matrix compound to a fibre-reinforced plastic profile and to define the outer geometry. Rovings or fabrics using thermoset matrix material can be processed, as well as tapes preimpregna-

ted with a thermoplastic matrix. As a restriction of the pultrusion process, it needs to be mentioned that the cross-section of the profiles always has to be constant. Therefore mainly tubes or rods with round or square cross-sections are manufactured by pultrusion, but also more complex geometries like window profiles. The state-of-the-art dimensions of these profiles range from about 5 millimetres up to several metres in diameter. The Fraunhofer IPT focuses on the pultrusion of miniaturized devices and the further development of the process. Currently, diameters down to 200 micrometres can be pultruded. These micro-diameter fibre-reinforced profiles can be used in many applications, for example in minimally invasive medical devices or as reinforcing elements. The mechanical properties of fibrereinforced plastic components are mainly defined by the choice of the reinforcing fibres, the fibre angle and the fibre volume content. Only rovings are used in micro-pultrusion, so that all filaments are arranged parallel to each other in the pulling direction. Due to the hexagonal packing of the

filaments, a fibre volume content higher than in any other production technologies for fibre-reinforced plastics can be reached. While a fibre volume content of about 90% is possible in theory, in practice Fraunhofer IPT has reached a

Fig. 1: Cross-section of a micro-pultruded GFRP profile

Fig. 2: Micro-pultrusion machine at Fraunhofer IPT

No73 June 2012

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JEC COMPOSITES MAGAZINE - Issue #73 - June 2012

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